Johnny Bohmer Proving Grounds was out to, err, prove something in its latest top speed run video. The car in question was a stock 2017 McLaren 570S, a twin-turbo supercar that makes as much as 562 horsepower (419 kilowatts) and 443 pound-feet (601 Newton-meters) of torque.
But this wasn’t about how fast this old McLaren could go. They went out to prove the inaccuracy in the car’s speedometer.
To measure that, Johnny Bohmer used three ways to measure speed: the car’s default speedometer, a Garmin VIRB GPS, and a Tag Heuer timing equipment used by the International Mile Racing Association.
The result? At 217 miles per hour (349 kilometers per hour) on the McLaren’s speedometer, the Garmin recorded 205 mph (330 km/h) while the IMRA tallied 205.596 mph (331 km/h) – a 12-mph (19 km/h) difference. It’s also worth noting that as the speed increases, the gap between the GPS reading and the speedometer increases, as seen in the video above.